Analogs of Manduca Adipokinetic-Hormone Tested in a Bioassay and in a Receptor-Binding Assay Single amino acid replacement analogs of Manduca adipokinetic hormone (M-AKH) pGlu-Leu-Thr-Phe-Thr-Ser-Ser-Trp-GlyNH2 were tested for activity in bioassays as well as receptor binding assays. Amino acids were replaced by Ala and by D-analogs. In addition an extended M-AKH and analogs containing photo affinity labels were tested. All analogs had reduced activity. All the peptides which had enough activity to allow a full dose response curve reached the same maximal activity as native M-AKH. The use of analogs, in which L-Phe4 was replaced by Ala or by D-Phe and L-Thr3 replaced by D-Thr, as competitors led to improved binding of M-AKH in our competitive receptor binding assays. In the bioassay an inactive concentration of Ala4 M-AKH increased the activity of a half optimal concentration of native M-AKH. Peptides, 19, 481-486 (1998).